“What we’re going to put on in July in the Senate is going to be unprecedented,” said Niger Innis, chief strategist of the group.

It’s unclear what role Sen. Rand Paul (R-Ky.) will play at the meeting. At a recent press conference on the IRS targeting tea party groups, Bachmann called Paul “the chair of the Tea Party Caucus in the U.S. Senate.”

An official Senate Tea Party Caucus does not yet exist, and Paul’s office did not respond to requests for comment on whether he would lead the meeting, but he did not dispute the title at the time.

Innis said that although the group is disappointed to see Bachmann leave Congress, her retirement will not affect the House group.

“I don’t think it’s going to affect the caucus at all,” Innis said. “She will certainly be missed. But the movement is just bigger than one, individual person. We look forward to working with her for the next year and a half and consulting with her as she passes the baton.

“I think she will continue to be an outstanding leader,” he added of Bachmann’s future role in the movement. “The tea party movement is just as important outside the Beltway as it is inside the Beltway.”

Roughly 20 House Republicans attended April’s closed-door caucus meeting led by Bachmann, along with staffers from nearly 40 congressional offices, including those of Paul and Senate Minority Leader Mitch McConnell.

Bachmann, facing investigations and a tough reelection race, announced early Wednesday that she would not seek a fifth term. Her retirement follows the departure of other tea party favorites — former Rep. Allen West (R-Fla.), who lost his seat in the 2012 election, and Sen. Jim DeMint (R-S.C.), who left to run The Heritage Foundation.